Method of manufacturing silicon nano-powders and manufacturing equipment implementing such method

This utility application claims priority to Taiwan Application Serial Number 111109170, filed Mar. 14, 2022, which is incorporated herein by reference.

The invention relates to a method of manufacturing a plurality of silicon nano-powders and a manufacturing equipment implementing such method, and more in particular, to a method of manufacturing a plurality of silicon nano-powders, with easy shape control, high purity and mass production, and a manufacturing equipment implementing such method.

High-purity silicon nano-powders have been used to manufacture many products with high commercial value, for example, for the production of hydrogen, for the manufacture of anodes of lithium-ion batteries, for the manufacture of silicon oxide and silicon carbide and so on.

Taking lithium-ion batteries as an example, lithium-ion batteries have been widely commercial energy storage devices. Lithium-ion batteries have the advantages of high energy density, high discharge voltage, small internal resistance, small self-discharge, no memory effect, and no pollution for environmental protection. Lithium-ion batteries have been widely used in various products in life, such as mobile phones, notebook computers, hearing aids, video cameras, electric vehicles, etc. In addition, lithium-ion batteries are also widely used in modern high-tech fields such as torpedoes, aircraft, and micro-electromechanical systems. Therefore, lithium-ion batteries are ideal new energy sources for human beings. However, there are still many deficiencies in currently commercial lithium-ion batteries, which make it impossible to meet the demand in the application of high specific energy power sources. As far as the anode is concerned, most of the currently commercial lithium-ion batteries use carbonaceous materials such as graphite as the anode. Because the anode made of graphite has the advantages of good conductivity and long cycle life. However, since the theoretical specific capacity of graphite is only 372 mAh/g, the specific capacity of the negative electrode made of graphite is low, which is far from meeting the capacity requirements of high specific energy power supply systems. Therefore, the development of anode materials with high capacity and excellent performance has become a current research hotspot.

Silicon has high theoretical lithium storage capacity, low lithium extraction potential (0.2-0.3V vs. Li/Li+), and silicon is an element with abundant reserves on the earth. Therefore, silicon is considered to be the most likely anode material to replace graphite. However, the large volume expansion (˜400%) of silicon anode in the process of lithiation/delithiation leads to the degradation of silicon particles and the destruction of the solid electrolyte interface. These problems can cause severe degradation of capacitance or even overall damage, which hinders the commercial application of silicon anodes in lithium-ion batteries.

But, a two-dimensional silicon nano-sheet material has the ability to resist expansion and fracture, and because it has a faster diffusion rate and a lower diffusion barrier of lithium ions, it has gradually been widely studied and applied to lithium ion battery anode materials.

Regarding the prior art of manufacturing silicon nano-sheets, please refer to Japanese Laid-Open Patent Publication No. 2008-069301. The prior art teaches first to produce layered polysilane powders represented by the compositional formula Si6H6 by reacting calcium disilicide with dense hydrogen chloride cooled below −30° C. The prior art then prepares silicon nano-sheets are prepared by reacting an organic compound having a carbon-carbon unsaturated bond with an organic group using a hydrosilylation reaction catalyst, and replacing the hydrogen atoms of the layered polysilane with an organic group. However, in layered polysilane powders, hydrogen atoms bonded to silicon atoms are easily replaced by hydroxyl groups. Therefore, the prior art does not benefit in purification and mass production of silicon nano-sheets.

In addition, most of the prior arts of manufacturing silicon nano-powders only manufacture silicon nano-powders with single shape, and cannot manufacture silicon nano-powders with different shapes for different product fields, such as a sphere, a wire, a flake etc.

In addition to the technology that benefits in the mass production of silicon nano-powders that still needs to be studied, the equipment that benefits in the mass production of silicon nano-powders also needs to be researched and developed, especially the manufacturing equipment that can manufactures silicon nano-powders with different shapes.

Accordingly, one scope of the invention is to provide a method of manufacturing a plurality of silicon nano-powders with easy shape control, high purity and mass production, and a manufacturing equipment implementing such method. The method according to the invention can manufacture a plurality of silicon nano-powders with high purity. The manufacturing equipment according to the invention is beneficial to the mass production of a plurality of silicon nano-powders with high purity.

A method of manufacturing a plurality of silicon nano-powders, according to a preferred embodiment of the invention, is, firstly, to prepare a plurality of aluminum powders and a silicon tetrahalide. Finally, the method according to the preferred embodiment of the invention is to heat the plurality of aluminum powders and the silicon tetrahalide to a reaction temperature such that the plurality of aluminum powders react with a reaction gas of the silicon tetrahalide into a plurality of silicon nano-powders and an aluminum trihalide, to obtain the plurality of silicon nano-powders.

In one embodiment, the reaction temperature ranges from 100° C. to 660° C.

4 4 4 4 In one embodiment, the silicon tetrahalide can be SiF, SiCl, SiBr, SiIor a mixture therebetween.

In one embodiment, an appearance of one of the plurality of silicon nano-powders exhibits a flake, a sphere, a wire, a tube and so on.

Further, the method according to the preferred embodiment of the invention is also to perform an acid washing treatment on the plurality of silicon nano-powders to purify the plurality of silicon nano-powders.

Further, the method according to the preferred embodiment of the invention is also to heat the plurality of silicon nano-powders and the aluminum trihalide to sublimate the aluminum trihalide, and further to purify the plurality of silicon nano-powders.

A manufacturing equipment for manufacturing a plurality of silicon nano-powders, according to a preferred embodiment of the invention, includes a furnace, a reactant supply source and a recovering apparatus. A plurality of aluminum powders are placed in the furnace. The reactant supply source communicates with the furnace, and is for supplying a silicon tetrahalide into the furnace. The recovering apparatus communicates with a top of the furnace. The furnace heats the plurality of aluminum powders and the silicon tetrahalide to a reaction temperature such that the plurality of aluminum powders react with a reaction gas of the silicon tetrahalide into a plurality of silicon nano-powders and an aluminum trihalide. The reaction temperature ranges from 100° C. to 660° C. The aluminum trihalide is sublimated and recovered by the recovering apparatus to obtain the plurality of silicon nano-powders.

Further, the manufacturing equipment according to a preferred embodiment of the invention also includes a stirring apparatus. The stirring apparatus is configured to operate within the furnace. The stirring apparatus stirs the plurality of aluminum powders during the reaction between the plurality of aluminum powders and the reaction gas.

Compared to the prior art, the method according to the invention can manufacture a plurality of silicon nano-powders with easy shape control, high purity and mass production. The manufacturing equipment according to the invention is beneficial to the mass production of a plurality of silicon nano-powders with high purity.

The advantage and spirit of the invention may be understood by the following recitations together with the appended drawings.

Some preferred embodiments and practical applications of this present invention would be explained in the following paragraph, describing the characteristics, spirit, and advantages of the invention.

1 FIG. 1 FIG. 1 Referring to,illustratively shows a method, according to the preferred embodiment of the invention, of manufacturing a plurality of silicon nano-powders.

1 FIG. 1 10 As shown in, the methodaccording to the preferred embodiment of the invention, firstly, performs step Sto prepare a plurality of aluminum powders and a silicon tetrahalide.

4 4 4 4 In one embodiment, the silicon tetrahalide can be SiF, SiCl, SiBr, SiIor a mixture therebetween.

1 12 Finally, the methodaccording to the preferred embodiment of the invention performs step Sto heat the plurality of aluminum powders and the silicon tetrahalide to a reaction temperature such that the plurality of aluminum powders react with a reaction gas of the silicon tetrahalide into a plurality of silicon nano-powders and an aluminum trihalide, to obtain the plurality of silicon nano-powders.

In one embodiment, the reaction temperature ranges from 100° C. to 660° C., which is lower than the melting point of aluminum.

4 4 3 Taking SiClas an example of silicon tetrahalide, the reaction between the plurality of aluminum powders and the reaction gas of silicon tetrahalide is represented by the following reaction formula:4Al(s)+3SiCl(g)→3Si(s)+4AlCl(s/g),ΔG=−218.6 KJ/mole (298 K)

4 4 4 4 3 It should be emphasized that the boiling point of SiFis −90.3° C., the boiling point of SiClis 56.8° C., the boiling point of SiBris 155.0° C., and the boiling point of SiIis 290.0° C. The boiling point of AlClis 183° C. Silicon tetrahalide is easy to supply in the form of gas, and aluminum trihalide is also easy to sublimate into gas to facilitate separation from silicon nano-powders.

In one embodiment, an appearance of one of the plurality of silicon nano-powders exhibits a flake, a sphere, a wire, a tube and so on. The shape of the plurality of silicon nano-powders depends on the shape of the plurality of aluminum powders used. To manufacture silicon nano-sheets, the aluminum powders used must be close to the shape and size of the silicon nano-sheets to be manufactured. The plurality of aluminum nano-sheets can be formed by rolling aluminum particles with appropriate particle size.

1 Further, the methodaccording to the preferred embodiment of the invention is also to perform an acid washing treatment on the plurality of silicon nano-powders to purify the plurality of silicon nano-powders.

1 Further, the methodaccording to the preferred embodiment of the invention is also to heat the plurality of silicon nano-powders and the aluminum trihalide to sublimate the aluminum trihalide, and further to purify the plurality of silicon nano-powders.

Regarding the implement of the method according to the invention, a plurality of aluminum powders and a silicon tetrahalide can be placed in a closed single autoclave reactor, and an inert atmosphere is introduced into the autoclave reactor or the interior of the autoclave reactor is evacuated into a vacuum environment, and then the interior of the autoclave reactor is heated up to the reaction temperature, such that the plurality of aluminum powders react with a reaction gas of the silicon tetrahalide into a plurality of silicon nano-powders and an aluminum trihalides. The pressure in the autoclave reactor is determined by the amount of silicon tetrahalide charged. The pressure during the reaction can range from 1 atm to 100 atm. The higher the pressure of the silicon tetrahalide vapor in the autoclave reactor is, the higher the reaction rate can be. After the temperature of the autoclave reactor is lowered, the plurality of silicon nano-powders are removed from the autoclave reactor, and then are performed an acid washing treatment to a plurality of purified silicon nano-powders. However, the production efficiency of the above approach is still low. Therefore, the invention also discloses a manufacturing equipment with high mass production efficiency.

2 FIG. 3 FIG. 4 FIG. 2 FIG. 2 FIG. 3 FIG. 4 FIG. 2 2 2 Referring,and,is a schematic diagram showing the architecture of a manufacturing equipmentaccording to the preferred embodiment of the invention. In, some devices and apparatuses are shown in cross-sectional view.is a schematic diagram showing the architecture of a modification of the manufacturing equipmentaccording to the preferred embodiment of the invention.is a schematic diagram showing the architecture of another modification of the manufacturing equipmentaccording to the preferred embodiment of the invention.

2 FIG. 2 20 24 26 As shown in, the manufacturing equipmentfor manufacturing a plurality of silicon nano-powders, according to the preferred embodiment of the invention, includes a furnace, a reactant supply sourceand a recovering apparatus.

20 202 24 20 24 20 242 24 20 26 20 26 20 262 2 FIG. 2 FIG. The furnaceincludes a heater. The reactant supply sourcecommunicates with the furnace. As shown in, the reactant supply sourcecommunicates with the furnacevia a first pipeline. The reactant supply sourceis used for supplying a silicon tetrahalide into the furnace. The recovering apparatuscommunicates with the top of the furnace. As shown in, the recovering apparatuscommunicates with the top of the furnacevia a second pipeline.

2 FIG. 2 27 27 26 2 264 264 262 26 27 20 27 20 Also as shown in, the manufacturing equipmentaccording to the preferred embodiment of the invention further includes a vacuum pumping apparatus. The vacuum pumping apparatusis communicated behind the recovering apparatus. The manufacturing equipmentaccording to the preferred embodiment of the invention further includes a control valve. The control valveis installed in the second pipeline. But the invention is not limited thereto. The recovering apparatusand the vacuum pumping apparatusmay communicate with the furnacerespectively. The vacuum pumping apparatusis used to pump the interior of the furnaceinto a vacuum environment.

2 FIG. 24 40 24 244 246 244 40 24 42 246 242 42 20 Also as shown in, the reactant supply sourcetherein contains a silicon tetrahalide liquid. The reactant supply sourceincludes a heaterand a control valve. The heateris used for heating the silicon tetrahalide liquidcontained in the reactant supply sourceto generate the silicon tetrahalide reaction gas. The control valveis installed in the first pipelineto control the reaction gasof silicon tetrahalide to flow into the furnace. But the invention is not limited thereto.

3 FIG. 3 FIG. 3 FIG. 2 FIG. 2 28 28 28 24 20 2 28 40 24 20 As shown in, he manufacturing equipmentaccording to the preferred embodiment of the invention further includes a pump. In, the pumpis a peristaltic pump, but the invention is not limited thereto. The pumpis connected between the reactant supply sourceand the furnace. The manufacturing equipmentaccording to the preferred embodiment of the invention can also use the pumpto feed the silicon tetrahalide liquidcontained in the reactant supply sourceinto the furnace. The devices and members inidentical to those shown inare given the same numerical notations, and will be not described in detail herein.

4 FIG. 4 FIG. 2 FIG. 2 29 29 20 292 2 294 294 292 29 20 As shown in, the manufacturing equipmentaccording to the preferred embodiment of the invention further includes a protection gas supply source. The protection gas supply sourcecommunicates with the furnacevia a third pipeline. The manufacturing equipmentaccording to the preferred embodiment of the invention further includes a control valve. The control valveis installed in the third pipeline. The protection gas supply sourceis used to supply a protection gas into the furnace, for example, neon, argon, nitrogen and so on. The devices and members inidentical to those shown inare given the same numerical notations, and will be not described in detail herein.

2 FIG. 3 FIG. 4 FIG. 2 22 22 20 22 Also as shown in,and, the manufacturing equipmentaccording to a preferred embodiment of the invention also includes a stirring apparatus. The stirring apparatusis configured to operate within the furnace. The stirring apparatusstirs the plurality of aluminum powders during the reaction between the plurality of aluminum powders and the reaction gas.

3 FIG. 5 FIG. 6 FIG. 2 32 Referring to,, andagain, by using the manufacturing equipmentaccording to the preferred embodiment of the invention, the manufacture of a plurality of silicon nano-powdersis described hereinafter.

3 FIG. 30 5 5 30 20 202 5 27 20 20 264 28 40 24 20 As shown in, a plurality of aluminum powdersare placed in a crucible, and then the cruciblecontaining the plurality of aluminum powdersis placed in the furnace. The heatersurrounds the outer wall of the crucible. The vacuum pumping apparatusfirst pumps the interior of furnaceinto a vacuum environment. After the furnaceis evacuated into the vacuum environment, the control valveis closed. The pumpfeeds the silicon tetrahalide liquidcontained in the reactant supply sourceinto the furnace.

5 FIG. 202 30 42 40 42 As shown in, the heaterheats the plurality of aluminum powdersand the reaction gasof the silicon tetrahalide to the reaction temperature. The reaction temperature ranges from 100° C. to 660° C. The silicon tetrahalide liquidevaporates into the reaction gasof the silicon tetrahalide.

6 FIG. 6 FIG. 30 42 30 42 32 44 32 44 20 30 42 30 42 30 32 30 42 22 30 30 42 As shown in, after the plurality of aluminum powdersand the reaction gasof the silicon tetrahalide are heated to the reaction temperature, the plurality of aluminum powdersand the reaction gasof silicon tetrahalide react into a plurality of silicon nano-powdersand the aluminum trihalide. In, only the plurality of silicon nano-powdersand the aluminum trihalidein the form of gas are shown in the furnace. The reaction temperature is held until the plurality of aluminum powderscompletely react with the reaction gasof the silicon tetrahalide. It is considered that the covered aluminum powdercannot contact and react with the reaction gasof the silicon tetrahalide when a large amount of aluminum powderis used to mass-produce a plurality of silicon nano-powders. Therefore, according to the invention, during the reaction between the plurality of aluminum powdersand the reaction gasof the silicon tetrahalide, the stirring apparatusstirs the plurality of aluminum powders, such that the plurality of aluminum powderscan contact and react with the reaction gasof the silicon tetrahalide as a whole, so as to realize mass production goals.

6 FIG. 44 44 32 44 26 26 44 266 Also as shown in, because the boiling point of the aluminum trihalideis lower than the reaction temperature ranging from 100 to 660° C., the aluminum trihalidewill sublimate into a gas and separate from the plurality of silicon nano-powders. The gaseous aluminum trihalideis recovered by the recovering apparatus. In one embodiment, the recovering apparatuscondenses the gas-forming aluminum trihalideby using the low-temperature water.

7 FIG. 9 FIG. 7 FIG. 7 FIG. 8 FIG. 8 FIG. 8 FIG. 4 In the first example, please refer toto, the method according to the invention is to prepare 0.4 g of aluminum powders and 2 g of SiCl. The aluminum powders used are high-purity aluminum powders which are originally used to manufacture a conductive aluminum paste. The shape of the used aluminum powders is close to spherical. The SEM photograph of the aluminum powders is shown in. In, the particle size of the used aluminum powder ranges from hundreds of nanometers to several micrometers. The used aluminum powders with a shape close to spherical are rolled into aluminum powders with a flake shape, and the SEM photograph of the rolled aluminum powders is shown in. The result of EDS analysis of the composition of the aluminum powders used is also shown in. In, the aluminum powders are in the form of flakes, and the aluminum powders used have high aluminum content percentage and small amounts of carbon and oxygen impurities.

4 4 4 4 3 9 FIG. 9 FIG. 10 FIG. 9 FIG. 10 FIG. Compared with the amount of aluminum powders to be reacted, the used SiClis about 10% in excess. 0.4 g of aluminum powders and 2 g of SiClare placed in an autoclave reactor with a capacity of 5 ml. By using the autoclave reactor, 0.4 g of aluminum powders and 2 g of SiClare heated to 300° C. for 10 hours, such that the aluminum powders react the reaction gas sublimated from SiClinto a plurality of silicon nano-powders and AlCl. The plurality of silicon nano-powders are taken out from the autoclave reactor, and then are pickled with 10 vol. % HCl acid solution for 5 minutes, and then are washed with clean water to purify the plurality of silicon nano-powders. The SEM photograph of the top surface of the purified silicon nano-powders is shown in. The composition result of the purified silicon nano-powders analyzed by EDS is also shown in. The SEM photograph of the side surface of the purified silicon nano-powders is shown in. In, the silicon nano-powders are in the shape of nano-sheets, and the purified silicon nano-powders have extremely high silicon content percentage, and have extremely small amounts of carbon, oxygen, aluminum, and chlorine impurities. In, the plurality of silicon nano-powders are shown with a thickness of about 80 nm. The first example described in the present invention is suitable for small-volume production of the plurality of silicon nano-powders.

8 FIG. 11 FIG. 12 FIG. 8 FIG. 3 FIG. 11 FIG. 12 FIG. 11 FIG. 12 FIG. 4 4 4 3 3 2 20 28 20 22 26 In the second example, please refer to,and, the method according to the invention is to prepare 15 g of aluminum powders and 55 g of SiCl. The SEM photograph and the composition result of the EDS analysis of the aluminum powders used are shown in. A plurality of silicon nano-powders are manufactured by using the manufacturing equipmentshown in. SiClis fed into the furnaceby means of the pump. The furnaceheats the aluminum powders and SiCl4 to 300° C. for 10 hours, such that the aluminum powders react with the reaction gas sublimated from SiClinto a plurality of silicon nano-powders and AlCl. During the reaction between the aluminum powders and the reaction gas, the stirring apparatusstirs the aluminum powders such that all of the aluminum powders can contact and react with the reaction gas of silicon tetrahalide. AlClwill be sublimated into gas and recovered by the recovering apparatus. The SEM photograph of the top surface of the plurality of manufactured silicon nano-powders is shown in. The SEM photograph of the side surface of the plurality of manufactured silicon nano-powders is shown in. In, the plurality of manufactured silicon nano-powders are in the form of nano-sheets. In, the plurality of manufactured silicon nano-powders show a thickness of about 40˜80 nm. The second example of the invention is suitable for mass production of a plurality of silicon nano-powders.

13 FIG. 14 FIG. 13 FIG. 14 FIG. The manufactured silicon nano-powders are pickled with 10 vol. % HCl acid solution, and then washed with clean water to purify the silicon nano-powders. The SEM photograph of the top surface of the purified silicon nano-powders is shown in. The SEM photograph of the side surface of the purified silicon nano-powder is shown in. In, the shape of the purified silicon nano-powders still maintains the shape of nano-sheets. In, the thickness of the nano-sheets of the purified silicon nano-powders does not change.

7 FIG. 15 FIG. 7 FIG. 3 FIG. 15 FIG. 15 FIG. 4 4 4 3 3 2 20 28 20 22 26 In the third example, please refer toand, the method according to the invention is to prepare 15 g of aluminum powders and 55 g of SiCl. The SEM photograph of the aluminum powders used are also shown in, that is to say, the aluminum powders whose shape is close to spherical are used. A plurality of silicon nano-powders are manufactured by using the manufacturing equipmentshown in. SiClis fed into the furnaceby means of the pump. The furnaceheats the aluminum powders and SiCl4 to 300° C. for 10 hours, such that the aluminum powders react with the reaction gas sublimated from SiClinto a plurality of silicon nano-powders and AlCl. During the reaction between the aluminum powders and the reaction gas, the stirring apparatusstirs the aluminum powders such that all of the aluminum powders can contact and react with the reaction gas of silicon tetrahalide. AlClwill be sublimated into gas and recovered by the recovering apparatus. The SEM photograph of the appearance of the plurality of manufactured silicon nano-powders is shown in. In, the shape of the plurality of silicon nano-powders is close to spherical.

With the detailed description of the above several examples of the invention, it can be proved that the method according to the invention can produce silicon nanometer powder with various shapes, high purity and large mass production.

With the detailed description of the above preferred embodiments of the invention, it is clear to understand that the method according to the invention can manufacture a plurality of silicon nano-powders with easy shape control, high purity and mass production. The manufacturing equipment according to the invention is beneficial to the mass production of a plurality of silicon nano-powders with high purity.

With the example and explanations above, the features and spirits of the invention will be hopefully well described. Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teaching of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.